The detection of light is used in a wide variety of applications. For example, light beams and corresponding light detectors are used to detect presence or encode motion. When light is incident on a light detector or photo-detector, it causes the detector to output an electronic signal that indicates that the beam of light has been received and may indicate the intensity or strength of the light received.
In some applications, it is desirable to detect light of a specific color or wavelength to assist in identifying components of a substance. Spectroscopy is also frequently used in astronomy and remote sensing.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.